A species of coin fraud has arisen in which the miscreant drills a hole through a coin of the type accepted by a coin-operated device, such as a coin telephone instrument, and attaches a flexible cord or string, such as monofilament fishing line, to the coin by threading the string through the drilled hole and knotting the end to tether the coin. The coin is then deposited in the coin slot, the tethered string allowing it to fall through the coin chute of the coin telephone instrument where it triggers the deposited coin registration switch if it is recognized as a genuine coin, or is rejected to the coin return bucket if determined to be counterfeit. In the latter case, the fraudulent user may attach a wad of material to the string and pull it back to jam the mechanism. This blocking of the coin return mechanism prevents subsequent legitimate users from receiving any refund of their mis-deposited coins and permits the miscreant to later return to the instrument, unblock its coin return path and receive the fraudulently stored coins. On the other hand, if the coin is recognized as valid, the coin will be held in escrow until a call is placed and has been answered. The fraudulent user, however, hangs up before answer is received, allowing the coin return hopper relay to be activated to return the coin. The fraudulent user now takes up all slack in the string to prevent the coin from returning, but keeping the coin below the release trap so the coin vane will be biased in the coin refund position. A new call may now be placed but, because the tethered string has fouled the apparatus, all deposited coins will be returned to the miscreant at the end of the call. It would be extremely advantageous to be able to frustrate both such fraudulent forms of usage.